1. Field of the Invention
The present invention relates to an optical disc, a reproduction apparatus, and a disc identifier selecting apparatus. The present invention also relates to an improvement in securing a copyright on data recorded on an optical disc.
2. Description of the Related Art
Manufacturers who record digital copyrighted materials, such as game software and movies, on optical discs pay great attention to the prevention of casual copying by ordinary users. The casual copying refers to user's operations where the users interconnect personal computers with commercially available reproduction apparatuses and recording apparatuses, read data from optical discs, such as CD-ROMs and DVD-ROMs, and write the read data on rewritable discs, such as hard disks CD-Rs, and DVD-Rs. As can be seen from this, the casual copying does not require specialized equipment and so it is possible for the users to perform the casual copying. If the casual copying is performed by many users, the optical disc industry will suffer great economical losses. Therefore, the manufacturers exert their best efforts to prevent the casual copying by processing digital copyrighted materials before recording the materials on optical discs. For instance, the digital copyrighted materials are encrypted using identification information unique to the optical discs.
Although having been effective until now, it cannot be ensured that this countermeasure will also be effective from now on because of the recent remarkable development in reverse techniques with which processes for encrypting the digital copyrighted materials are analyzed. If an analyzing program that analyzes the encryption processes and decrypts encrypted materials is developed and distributed to the ordinary users, the users can copy the digital copyrighted materials with a system composed of personal computers on which the analyzing program has been installed and commercially available reproduction apparatuses and recording apparatuses. As is understood from this, the emergence of the analyzing program makes it impossible to prevent the casual copying with the currently used technique. This means that the currently used technique of securing copyrights on digital copyrighted materials cannot be said as a complete countermeasure against the casual copying.